Film thrusting cassette

ABSTRACT

In a film cassette, a film spool comprises a spool core supported for rotation in an unwinding direction to thrust a leader section of a filmstrip coiled about the spool core from the cassette and in a winding direction to return the leader to the cassette, and a pair of flanges positioned along the spool core to overlie opposite sides of the film roll. The flanges have respective central openings through which the spool core axially extends to normally permit each of the flanges to be independently rotated relative to the spool core in the unwinding and winding directions. According to the invention, the spool core includes a core piece connected to a remaining portion of the spool core for limited movement within the central opening of one of the flanges, away from the remaining portion, to engage the flange to rotate the flange in unity with the spool core when the spool core is rotated in the unwinding direction, to improve the ability of the film spool to thrust the leader from the cassette, and toward the remaining portion, to disengage the flange to permit the flange to be independently rotated when the spool core is rotated in the winding direction.

CROSS-REFERENCE TO RELATED APPLICATIONS

Reference is made to commonly assigned copending applications Ser. No. 07/320,440, entitled FILM CASSETTE, and filed Mar. 8 the name of John J. Niedospial; Ser. No. 07/415,750 entitled FILM CASSETTE, and filed Sept. 27, 1989 in the name of J. Niedospial; al Ser. No. 07/464,048 entitled FILM CASSETTE, and filed Jan. 12, 1990 in the names of Michael T. Wolf et al and Ser. No. 07/464,264 entitled FILM CASSETTE, and filed Jan. 12, 1990 in the names of Edward H. Dowling et al.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates generally to the field of photography, and particularly to a film cassette containing roll film. More specifically, the invention relates to a film cassette that is capable of automatically advancing a non-protruding film leader to the exterior of the cassette shell responsive to unwinding rotation of a film spool within the shell.

2. Description of the Prior Art

In conventional 35mm film manufacturers' cassettes, such as manufactured by Eastman Kodak Co. and Fuji Photo Film Co. Ltd., the filmstrip is wound on a flanged spool which is rotatably supported within a cylindrical shell. A leading or forward-most section of the filmstrip approximately 2 1/3 inches long, commonly referred to as a "film leader", normally protrudes from a light-trapped slit or mouth of the cassette shell. One end of the spool has a short axial extension which projects from the shell, enabling the spool to be turned by hand. If the spool is initially rotated in an unwinding direction, the film roll inside the shell will tend to expand radially since the inner end of the filmstrip is attached to the spool, and the fogged leader section protruding from the slit will remain stationary. The film roll can expand radially until a firm non-slipping relation is established between its outermost convolution and the inner curved wall of the shell. Once this non-slipping relation exists, there is a binding effect between the film roll and the shell which prevents further rotation of the spool in the unwinding direction. Thus, rotation of the spool in the unwinding direction cannot serve to advance the filmstrip out of the shell, and it is necessary in the typical 35mm camera to engage the protruding leader section to draw the filmstrip out of the shell.

A 35mm film cassette has been proposed which, unlike conventional film cassettes, can be operated to automatically advance a film leader out of the cassette shell by rotating the film spool in the unwinding direction. The film leader originally is located entirely inside the cassette shell. Specifically, in U.S. Pat. No. 4,423,943, granted Jan. 3, 1984, there is disclosed a film cassette wherein the outermost convolution of the film roll wound on the film spool is radially constrained by respective circumferential lips of two axially spaced flanges of the spool to prevent the outermost convolution from contacting an inner curved wall of the cassette shell. The trailing end of the filmstrip is secured to the film spool, and the forward or leading end of the filmstrip is slightly tapered purportedly to allow it to freely extend from between the circumferential lips and rest against the shell wall at a location inwardly of a non-lightweight film passageway to the outside of the cassette shell. During initial unwinding rotation of the film spool, the leading end of the filmstrip is advanced along the shell wall until it reaches an inner entrance to the film passageway. Then, it is advanced into and through the film passageway to the outside of the cassette shell. The passageway has a width that is less than the width of the filmstrip, thus resulting in the filmstrip being transversely bowed as it is uncoiled from the film spool, and thereby facilitating movement of the film edges under the circumferential lips of the flanges. However, severe transverse bowing of the filmstrip in order to move its longitudinal edges under the circumferential lips of the flanges may damage the filmstrip.

Like the type of film cassette disclosed in U.S. Pat. No. 4,423,923, commonly assigned Pats. No. 4,834,306 granted May 30, 1989, and No. 4,848,693, granted July 18, 1989, each disclose a film cassette that is capable of automatically advancing a non-protruding film leader to the outside of the cassette shell in response to rotation of the film spool in the unwinding direction. Specifically, there is disclosed a film cassette wherein a film roll is wound on a spool between a pair of coaxially spaced, independently rotatable flanges. The two flanges have respective circumferential annular lips which prevent the outermost convolution of the film roll, including its leading end, from clock-springing into contact with the interior wall of the cassette shell. When the spool is initially rotated in the unwinding direction, the flanges may momentarily remain stationary and the film roll, since its inner end is secured to the spool, tends to expand radially to ensure a firm non-slipping relation between the outermost convolution and the annular lips. Once the non-slipping relation exists, continued rotation of the spool will similarly rotate the flanges. This allows stationary internal spreaders to deflect successive portions of the annular lips to an axial dimension exceeding the film width, in turn allowing the leading end and successive sections of the film roll to be freed from the radial confinement of the annular lips and to be advanced into and through a lighttight film passageway to the outside of the cassette shell. A stripper-guide located adjacent an inner entrance to the film passageway diverts the leading end of the film roll into the passageway by being received between the leading end and the next-inward convolution of the film roll responsive to unwinding rotation of the spool.

The Cross-Referenced Applications

Cross-reference Applications Ser. No. 07/320,440 and No. 07/415,750 each disclose a film cassette wherein a film roll whose outermost convolution is a film leader is coiled about a spool rotatable within the cassette shell, a pair of flexible independently rotatable flanges are coaxially arranged on the spool to radially confine the film leader within respective skirted peripheries of the flanges to prevent the leader from substantially contacting an interior wall of the cassette shell, and a film stripper-guide projecting from the interior wall is received between a leading end of the film leader and the next-inward convolution of the film roll to free the leader from the flanges and guide the leader through a lighttight film passageway to the exterior of the cassette shell responsive to rotation of the spool in a film unwinding direction. Specifically, the stripper-guide frees the film leader from the flexible flanges by inducing the leader to flex the flanges away from one another at their skirted peripheries during unwinding rotation of the spool. Moreover, the film leader and at least one of the flanges include mutual engagement means for maintaining the leading end of the leader spaced at least a minimum radial distance from the next-inward convolution of the film roll sufficient to locate the leading end within range of the stripper-guide, to ensure that the leading end will be advanced over the stripper-guide responsive to rotation of the spool in the film unwinding direction.

SUMMARY OF THE INVENTION

According to the invention, it has been found that by fixing at least one of the film confining flanges to the film spool during unwinding rotation of the spool, as contrasted with allowing each of the flanges to remain rotatable independently of the spool as in commonly assigned U.S. Pats. No. 4,834,306 and No. 4,848,693 and in cross-reference applications Serial No. 07/320,440 and No. 07/415,750, there is immediately effected a frictional relationship between the outermost convolution of the film roll and the skirted periphery of the fixed flange which improves the ability of the spool to thrust the film leader through the lighttight passageway to the exterior of the cassette shell. In particular, the frictional relationship increases the pushing force the spool will apply to the film leader to propel the leader out of the cassette shell. Moreover, it has been found that by allowing both of the flanges to be rotated independently of the spool during winding rotation of the spool, as in commonly assigned U.S. Pats. No. 4,834,306 and No. 4,848,693 and in cross-referenced applications Serial No. 07/320,440 and No. 07/415,750, it is substantially ensured that the leader can be rewound within the skirted peripheries of the flanges without being obstructed by the skirted peripheries.

Thus, the invention may be summarized as follows:

In a film cassette, a film spool comprising (a) a spool core supported for rotation in a film unwinding direction to thrust a leader section of a filmstrip coiled about the spool core to the exterior of the cassette and in a film winding direction to return the leader to the interior of the cassette, and (b) a pair of flanges positioned along the spool core to overlie opposite sides of the film roll to radially confine the film roll within skirted peripheries of the flanges and having respective central openings through which the spool core axially extends to normally permit each of the flanges to be independently rotated relative to the spool core in the film unwinding and film winding directions, is characterized in that:

the spool core includes a core piece connected to a remaining portion of the spool core for rotation within the central opening of one of the flanges, relative to the remaining portion substantially in the film unwinding direction, to engage the flange to rotate the flange in unity with the spool core when the spool core is rotated in the film unwinding direction, to improve the ability of the film spool to thrust the leader from the cassette, and relative to the remaining portion substantially in the film winding direction, to disengage the flange to permit the flange to be independently rotated when the spool core is rotated in the film winding direction, to generally ensure the leader can be rewound within the skirted periphery of the flange.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded perspective view of a film cassette according to a preferred embodiment of the invention;

FIG. 2 is an elevation view of the film cassette, illustrating the cassette shell open to reveal a film roll coiled about a film spool;

FIG. 3 is an end view partly in cross-section of the cassette shell, the film roll and the film spool, illustrating the manner in which the film roll is originally stored on the film spool;

FIGS. 4, 5, 6 and 7 are end views similar to FIG. 3, illustrating the manner in which the film roll is unwound from the film spool;

FIGS. 8 and 9 are elevation views of the film roll and the film spool, illustrating the manner in which the film roll is originally stored on the film spool;

FIGS. 10 and 11 are elevation views similar to FIGS. 8 and 9, illustrating the manner in which the film roll is unwound from the film spool;

FIGS. 12 and 13 are elevation views in section of the film roll and the film spool, illustrating the manner in which one of a pair of film confining flanges of the spool may be fixed to the spool for concurrent rotation with the spool; and

FIGS. 14 and 15 are cross-section views as seen in the direction of the arrows 12,12 and 13,13 in FIGS. 12 and 13 respectively.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The invention is disclosed as being embodied preferably in a 35mm film cassette. Because the features of this type of film cassette are generally well known, the description which follows is directed in particular to elements forming part of or cooperating directly with the disclosed embodiment. It is to be understood, however, that other elements not specifically shown or described may take various forms known to persons of ordinary skill in the art.

Referring now to the drawings, FIGS. 1, 2 and 12 depict an improved 35mm film cassette 1 comprising a lighttight cassette shell 3 and a film spool 5 which is rotatable about an axis X in film unwinding and film winding directions U and W within the cassette shell. The cassette shell 3 consists of two shell halves 7 and 9 which are mated along respective grooved and stepped edge portions 11 and 13. The mated halves 7 and 9 define upper and lower aligned circular openings 15 and 17 for relatively shorter and longer opposite open-end extensions 19 and 21 of a spool core or hub 23, and they define a narrow relatively-straight film passageway 25 to the exterior of the cassette shell 3. The spool core 23 is a two-piece assembly comprising a relatively longer core piece 26 including the shorter end extension 19 and a relatively short core piece 27 including the longer end extension 21. The shorter core piece 27 is supported via an integral spindle 28, received in an eccentric or non-coaxial bore 29 in the longer core piece 26, for rotation in opposite directions U' and W' substantially similar to the film unwinding and film winding directions U and W, about an axis X' extending parallel to the axis X. The shorter core piece 27 and the longer core piece 26 each include an annular peripheral groove 30 which mates with a corresponding edge portion 31 of the respective openings 15 and 17 in the cassette shell 3 to rotatably support the film spool 5 for rotation about the axis X in the film unwinding and film winding directions U and W. A known black velvet or plush material 32 lines the interior of the film passageway 25 to prevent ambient light from entering the film passageway.

A roll 33 of 35mm filmstrip F is coiled about the longer piece 26 of the spool core 23 to form successive film convolutions. As shown in FIG. 3, the film roll 33 includes an outermost convolution which comprises a film leader 35 having a leading or forward end section 37, and it includes a next-inward convolution 39 coiled behind the outermost convolution. The inner or trailing end section of an innermost convolution 40 of the film roll 33 is secured to the longer core piece 26 using known attachment means, not shown. See FIG. 12.

A pair of upper and lower identical, very thin, flexible film confining flanges 41 and 43 are coaxially spaced along the spool core 23 as shown in FIGS. 1, 2, 8 and 12. The two flanges 41 and 43 comprise respective integral disks 45 and 47 and respective integral annular lips or skirts 49 and 51 which circumferentially extend from the disks. The two disks 45 and 47 cover opposite substantially flat sides of the film roll 33 which are defined by corresponding opposite longitudinal edges 53 and 55 of each successive convolution of the film roll, and they have respective central holes 56 through which the longer and shorter pieces 26 and 27 of the spool core 23 axially extend to permit rotation of the spool core relative to the flanges 41 and 43. See FIG. 12. The longer core piece 26 has a peripheral groove 57 for supporting the flange 41 in the groove to permit the flange to be independently rotated relative to the spool core 23 in the film unwinding and film winding directions U and W. The shorter core piece 27 and the longer core piece 26 have a common or in-line peripheral groove 58 for supporting the flange 43 in the groove to permit the flange to be independently rotated relative to the spool core 23 in the film unwinding and film winding directions U and W. The two grooves 57 and 58 are sufficiently spaced from one another along the spool core 23 to maintain respective inner faces 45' and 47' of the disks 45 and 47 spaced from the longitudinal edges 53 and 55 of each successive convolution of the film roll 33. See FIG. 12. The annular lips 49 and 51 overlap the film leader (outermost convolution) 35 of the film roll 33 radially outward of the longitudinal edges 53 and 55 of the leader to radially confine the leader to thus prevent it from radially expanding or clock-springing into substantial contact with an interior curved wall 59 of the cassette shell 3. A lip-receiving notch 60 is cut in the film leader (outermost convolution) 35 along its longitudinal edge 55, relatively close to its leading end 37, to receive a peripheral section 51' of the annular lip 51. This allows a relatively short edge-section 61 of the film leader (outermost convolution) 35 connecting the leading end 37 and the notch 59 to overlap the annular lip 51 radially outward to thus maintain the leading end spaced a radial distance D from the next-inward convolution 39 of the film roll 33. See FIGS. 4 and 9. The leading end 37 has a forward edge 63 inclined from the longitudinal edge 53 of the film leader (outermost convolution) 35 to the other longitudinal edge 55 of the leader to form a forward-most tip or tab 65 of the leader which, like the edge-section 61, overlaps the annular lip 51 radially outward. See FIGS. 1, 2, 8 and 9.

A film stripper-guide 67 projecting from the interior wall 59 of the cassette half 7 is positioned immediately inward of the inner entrance to the film passageway 25 to be received between the leading end 37 of the film leader (outermost convolution) 35 and the next-inward convolution 39, close to the forward-most tip 65 of the leader, to pick up the leading end and guide it into the film passageway responsive to rotation of the spool core 23 in the unwinding direction U. See FIGS. 1, 4-7, 10 and 11. The leading end 37 will be advanced over the stripper-guide 67 and into the film passageway 25, rather than between the stripper-guide and the next-inward convolution 39, because it is spaced the radial distance D from the latter convolution. Thus, as shown in FIG. 4, the leading end 37 will be located within range of the stripper-guide 67 due to such spacing D from the next-inward convolution 39.

When the leading end 37 of the film leader (outermost convolution) 35 is advanced over the stripper-guide 67 responsive to rotation of the spool core 23 in the unwinding direction U, the longitudinal edges 53 and 55 of the leader start to gently flex respective arcuate portions of the two flanges 41 and 43 axially away from one another, first to allow the notch 59 to separate from the lip section 51', and then to allow successive longitudinal sections of the leader to exit from between the flanges to the outside of the cassette shell 3. See FIGS. 10 and 11. The local flexing of the flanges 41 and 43 occurs because the film width W_(F) between the longitudinal film edges 53 and 55 is slightly greater than the axial spacing A_(S) between the annular lips 49 and 51. Moreover, successive convolutions of the film roll 33 have a resistance to transverse bowing that is greater than the resistance of the flanges 41 and 43 to be locally flexed. A pair of flat curved bearing members 69 extend from the interior wall 59 of the cassette shell 3 to lie flatly against successive arcuate portions of the two disks 45 and 47 as the flanges 41 and 43 are locally flexed axially away from one another, to thereby assure return of the flexed portions of the flanges to their normal original non-flexed condition. See FIGS. 1 and 2.

A film flattening member 71 projects from the interior wall 59 of the cassette half 9 in the vicinity of the inner entrance to the film passageway 25 and the stripper-guide 67 to support successive longitudinal sections of the film leader 35, beginning with its leading end 37, substantially flat as those sections are freed from the flanges 41 and 43, to facilitate movement of the leading end into the passageway. See FIGS. 6 and 7. The light-trapping plush 32 within the film passageway 25 is elevated along the passageway slightly beyond a longitudinal center line L of the passageway. The film flattening member 71 as shown in FIG. 3 projects almost to the center line L in order to support successive sections of the film leader 35 substantially flat at the center line. See FIGS. 6 and 7. Preferably, a substantially planar film-supporting face 73 of the flattening member 71 is spaced 0.005"-0.030" short of the center line L, and extends widthwise of the film passageway 25 as shown in FIG. 1.

A slot 75 is cut in the film leader (outermost convolution) 35 substantially proximate its leading end 37. A tooth 77 fixed to the interior wall 59 of the cassette half 7 has a free pointed end 79 which is positioned to be received in the slot 75 to thus engage the film leader (outermost convolution) 35, when the spool core 23 is rotated in the winding direction W as shown in FIG. 3, and to exit the slot to thus disengage the leader, when the film spool is rotated in the unwinding direction U as shown in FIG. 4. The engagement of the film leader (outermost convolution) 35 and the tooth 77 responsive to rotation of the film spool 5 in the winding direction W prevents the leading end 37 of the leader from coming to rest between the stripper-guide 67 and the next-inward convolution 39.

Operation

If the shorter piece 27 of the spool core 23 is initially rotated relative to the longer piece 26 of the spool core about the axis X' substantially in the film unwinding direction U, i.e. in the particular direction U. shown in FIGS. 13 and 15, for example by engaging a keying member 81 within the open-end extension 21 of the shorter core piece, the shorter core piece will move slightly outward of the curved periphery of the longer core piece, at a location adjacent their common groove 58, to change to a peripheral non-conformity with the longer core piece, thereby to engage the disk 47 of the flange 43 along the groove to fix the flange to the longer and shorter core pieces. At this time, a stop wall 82 of the shorter core piece 27 will have swung into abutment with a corresponding wall 83 of the longer core piece 26 to prevent further rotation of the shorter core piece relative to the longer core piece substantially in the film unwinding direction U, i.e. in the particular direction U. See FIG. 15. Then, continued rotation of the shorter core piece 27 will similarly rotate the spool core 23, including the longer core piece 26 and the flange 43, about the axis X in the film unwinding direction U. See FIGS. 4-7, 10 and 11. As a result, the film leader (outermost convolution) 35 will be advanced off the tooth 77 and its leading end 37 will be advanced over the stripper-guide 67, causing successive arcuate portions of the flanges 41 and 43 to be flexed axially away from one another as shown in FIG. 11. This first allows the notch 60 in the film leader (outermost convolution) 35 to separate from the lip section 51' of the flange 43, and then it allows successive longitudinal sections of the film leader to exit from between that flange and the flange 41 to the outside of the cassette shell 3. Since the stripper-guide 67 initially picks up the leading end 37 of the film leader 35 close to its forward-most tip 65, the forward edge 63 of the leading end might initially be supported along a narrow ridge 85 forming one end of the interior wall 59 of the cassette half 7. However, the leading end 37 will tend to back away from the ridge 85 and move against the film-supporting face 73 of the flattening member 71 as shown in FIG. 6.

If the shorter piece 27 of the spool core 23 is rotated relative to the longer piece 26 of the spool core about the axis X' substantially in the film winding direction W, i.e. in the particular direction W' shown in FIGS. 13 and 15, by engaging its keying member 81, after some length of the filmstrip F has been advanced from the cassette shell 3, the shorter core piece will move slightly inward of the curved periphery of the longer core piece, at a location adjacent their common groove 58, to return to a peripheral conformity with the longer core piece, thereby to release or disengage the disk 47 of the flange 43, to thereafter permit the flange to be rotated independently of the spool core. At this time, the stop wall 82 of the shorter core piece 27 will have separated from the corresponding wall 83 of the longer core piece 26, and instead a stop wall 87 of the shorter core piece will have swung into abutment with a corresponding wall 89 of the longer core piece to prevent further rotation of the shorter core piece relative to the longer core piece substantially in the film winding direction W, in the particular direction W'. See FIG. 14. Then, continued rotation of the shorter core piece 27 will similarly rotate the spool core 23, including the longer core piece, in the film winding direction W to rewind the filmstrip F onto the spool core. The spool core 23 is rotated in the film winding direction W substantially until the slot 75 in the film leader (outermost convolution) 35 receives the free end 79 of the tooth 77 to thereby re-engage the film leader to the tooth.

According to the invention, it has been found that by fixing the flange 43 to the spool core 23 during unwinding rotation of the film spool 5, as contrasted with allowing that flange to remain rotatable independently of the spool core as in commonly assigned U.S. Pats. No. 4,834,306 and No. 4,848,693, there is immediately effected a frictional relationship between the film leader (outermost convolution) 35 and the skirted periphery 51 of the fixed flange which improves the ability of the film spool to thrust the film leader through the lighttight passageway 25 to the exterior of the cassette shell 3. In particular, the frictional relationship increases the pushing force the spool core 23 will apply to the film leader 35 to propel the leader out of the cassette shell 3. Moreover, it has been found that by allowing both of the flanges 41 and 43 to be rotated independently of the spool core 23 during winding rotation of the film spool 5, as in commonly assigned U.S. Pats. No. 4,4834,306 and No. 4,848,693, it is substantially ensured that the leader can be rewound within the skirted peripheries 49 and 51 of the flanges without being obstructed by the skirted peripheries.

The invention has been described with reference to a preferred embodiment. However, it will be appreciated that variations and modifications can be effected within the ordinary skill in the art without departing from the scope of the invention. For example, both of the flanges 41 and 43 might be fixed to the spool core 23 during unwinding rotation of the spool core, rather than only one of the flanges being fixed to the spool core as in the preferred embodiment. 

We claim:
 1. In a film cassette, a film spool comprising (a) a spool core supported for rotation in a film unwinding direction to thrust a leader section of a filmstrip coiled about said spool core to the exterior of said cassette and in a film winding direction to return said leader to the interior of the cassette, and (b) a pair of flanges positioned along said spool core to overlie opposite sides of said film roll to radially confine the film roll within skirted peripheries of said flanges and having respective central openings through which the spool core axially extends to normally permit each of the flanges to be independently rotated relative to the spool core in the film unwinding and film winding directions, is characterized in that:said spool core includes a core piece connected to a remaining portion of the spool core for rotation within the central opening of one of said flanges, relative to said remaining portion substantially in the film unwinding direction, to engage the flange to rotate the flange in unity with the spool core when the spool core is rotated in the film unwinding direction, to improve the ability of said film spool to thrust said leader from said cassette, and relative to the remaining portion substantially in the film winding direction, to disengage the flange to permit the flange to be independently rotated when the spool core is rotated in the film winding direction, to generally ensure the leader can be rewound within said skirted periphery of the flange.
 2. A film cassette as recited in claim 1, wherein said core piece is connected eccentrically to the remaining portion of said spool core to move outward of a curved periphery of said remaining portion, to engage one of said flanges, responsive to rotation of the core piece relative to the remaining portion substantially in the film unwinding direction and to return at least to said curved periphery of the remaining portion, to disengage the flange, responsive to limited rotation of the core piece relative to the remaining portion substantially in the film winding direction.
 3. A film cassette as recited in claim 1 or 2, wherein said core piece and the remaining portion of said spool core have a common peripheral groove for supporting one of said flanges in said groove to permit the flange to be independently rotated relative to the spool core in the film unwinding and film winding directions.
 4. A film cassette as recited in claim 1, 2 or 3, wherein said core piece is connected to the remaining portion of said spool core for limited rotation relative to the remaining portion substantially in the film unwinding and film winding directions about an axis extending parallel to the axis the spool core is rotated in the film unwinding and film winding directions.
 5. A film cassette as recited in claim 1, wherein said core piece is connected to the remaining portion of said spool core to change to a peripheral non-conformity with said remaining portion, to engage one of said flanges, responsive to limited rotation of the core piece relative to the remaining portion substantially in the film unwinding direction and to return to peripheral conformity with the remaining portion, to disengage the flange, responsive to limited rotation of the core piece relative to the remaining portion substantially in the film winding direction.
 6. A film cassette as recited in claim 5, wherein said core piece is connected eccentrically to the remaining portion of said spool core for limited rotation of the core piece relative to the remaining portion substantially in the film unwinding and film winding directions.
 7. A film cassette as recited in claim 1, wherein said core piece and the remaining portion of said spool core include respective stop surfaces that abut responsive to limited rotation of the core piece relative to said remaining portion in the film unwinding and winding directions to prevent further rotation of the core piece relative to the remaining portion in the two directions, though allowing joint rotation of the core piece and the remaining portion in those directions.
 8. In a film cassette, a film spool comprising (a) a spool core supported for rotation in a film unwinding direction to thrust a leader section of a filmstrip coiled about said spool core to the exterior of said cassette and in a film winding direction to return said leader to the interior of the cassette, and (b) a pair of flanges positioned along said spool core to overlie opposite sides of said film roll and having respective central openings through which the spool core axially extends to normally permit each of the flanges to be independently rotated relative to the spool core in the film unwinding and film winding directions, is characterized in that:said spool core includes a core piece connected to a remaining portion of the spool core for limited movement within the central opening of one of said flanges, away from said remaining portion, to engage the flange to rotate the flange in unity with the spool core when the spool core is rotated in the film unwinding direction, to improve the ability of said film spool to thrust said leader from said cassette, and toward the remaining portion, to disengage the flange to permit the flange to be independently rotated when the spool core is rotated in the film winding direction.
 9. A film cassette as recited in claim 8, wherein said core piece is connected to the remaining portion of said spool core to change to a peripheral non-conformity with said remaining portion, to engage one of said flanges, responsive to limited movement of the core piece away from said remaining portion, and to return to a peripheral conformity with the remaining portion, to disengage the flange, responsive to limited movement of the core piece toward the remaining portion. 